The present invention relates to an axial fan, a method of manufacturing an impeller for the axial fan, and a mold for manufacturing the impeller of the axial fan and, more particularly, to a technology concerning an axial fan having an impeller that can obtain a sufficiently large air flow and wind pressure regardless of its compact, flat shape.
In an axial fan, an impeller, which is formed by arranging a plurality of vanes on the outer circumferential surface of a rotor having a permanent magnet on its inner circumference, is supported to be rotatable about the main body side stator of the axial fan. When a rotating magnetic field is generated in the stator, a desired air flow and wind pressure are obtained upon rotation of the rotor. Since the axial fan can be made compact and flat, it is incorporated mainly in an electronic equipment which is formed compact and flat, to prevent an increase in temperature (caused by heat generated by an internal electronic circuit board and the like.
Further downsizing and flattening of the axial fan are demanded in order to cope with recent size reduction of electronic equipments. The reduction in air flow and wind pressure upon such downsizing and flattening is not allowable. Therefore, various proposals have been made concerning an axial fan in order to ensure a large air flow and wind pressure.
"A Compact Blower" disclosed in Japanese Patent Publication No. 4-502052 is a proposal for performing downsizing and flattening while ensuring an air flow and wind pressure. According to this proposal, the vanes of an axial fan having an impeller are integrally molded so as to extend towards the central portion of the base portion of the impeller. When the axial fan is formed in this manner, a decrease in air flow caused by a decrease in outer diameter of the impeller and in area of the vanes as the result of downsizing can be prevented.